It's springtime, and those passionate penguins will soon be a it again at the Baltimore Zoo's Rock Island exhibit, site of the nation's most successful captive breeding program for an endangered species from South Africa.
The zoo's black-footed penguin colony, the largest in the country, is preparing for courtship. Over the next few weeks, the penguins will turn their exhibit into a kind of Poconos honeymoon retreat.
That suits zoo keepers just fine. Penguin-breeding is "one of our top priorities," said Steven J. Sarro, the zoo's senior keeper for birds. Zoo wildlife specialists have been encouraging the penguins' rites of spring for 25 years now, he noted, "and they've been very astute."
Starting in 1967 with 18 birds captured in the wild, Baltimore's black-footed penguins have produced about 600 offspring. The zoo, in turn, has sold and shipped 275 to zoos elsewhere in the United States -- including zoos in the Ohio cities of Toledo and Columbus, and in Mystic, Conn.
Another 78 have migrated to six foreign zoos, as far afield as the Budapest Zoological and Botanical Gardens in Hungary and the Agricolla Todini of Todi, Italy.
Zoo officials figure that 66 percent of the black-footed penguins in U.S. zoos are descended from the first birds to set foot on Rock Island's concrete shoreline.
Like good hostelers anywhere, Baltimore zoo keepers have left nothing to chance. They've paid painstaking attention to the diets, health and mating preferences of their guests.
"The biggest thing that we do is keep unbelievably detailed records," Mr. Sarro said. "With that, you can check on a daily basis what each bird is consuming, how it's behaving, who it's interacting with."
When a male and a female begin to court, zoo keepers check their ancestry to determine if the animals are too closely related to make a good match. If so, they are separated and paired with more suitable mates.
Mating pairs generally produce two eggs a year, usually in late June or July. Three weeks after the chicks hatch, zoo keepers remove them from the colony and take them to the zoo hospital, where they are fed by hand until they are 12 weeks old.
During this period, chicks are given blood tests every two weeks to determine if they have contracted avian malaria. The parasite-caused disease is common in this country but does not exist in Africa.
There is no vaccine to prevent chicks from catching the illness, which, like human malaria, is transmitted by mosquitoes. But sick birds can be treated with drugs.
"Health-wise, it's just easier to monitor the birds," Mr. Sarro said. The 2 1/2 months of isolation also shield the chicks from inadvertent injury during the brawls that occasionally break out among disgruntled Rock Island denizens.
Catering is a big concern. At Rock Island, penguins feast on farm-raised trout, squid, river smelt and capelin (another variety of herring).
While human newlyweds cuddle in hotel rooms with heart-shaped tubs and ceiling mirrors, the zoo's penguin couples get passionate in 18 plastic sky kennels, used to ship dogs aboard airplanes, lined up in a room built inside Rock Island.
Air conditioning isn't needed at Rock Island during Baltimore's sweltering summers. That's because black-footed penguins, unlike the species that live in Antarctica, have bald spots in their insulating plumage that allow them to slough off body heat.
The birds are adapted to both extremes of temperature. Their island homes are often hot, while the waters off South Africa are very cold.
Because of their success as matchmakers, Baltimore zoo keepers maintain the nation's stud book for penguin species. The book lists the genealogical history of all the breeding-age birds in the United States, and is used by zoos to find eligible partners for their own birds.
Rock Island generates income for the zoo through the sale of offspring to other zoos. (Zoo officials declined to discuss prices). More important, the communal love nest helps ensure the survival of the species, Spheniscus demersus.
Once millions of wild black-footed penguins bobbed and dove in the waters off South Africa. But oil spills and overfishing have reduced their numbers to a few hundred thousand, Mr. Sarro said. Now the birds are in danger of becoming extinct in the wild.
Extinction is not a concern on Rock Island.
Normally, Mr. Sarro said, the penguins don't get amorous until June or July. But this year, some frisky birds have gotten a head start. One pair produced its first egg in the past few weeks, he noted.
THE BLACK FOOTED PENGUIN (Spheniscus Demersus)
Habitat: The Dassen Islands and other islands off the coast of South Africa.
Characteristics: Stolid, muscular birds with sharp beaks. About 18 inches tall. Weigh 8-10 pounds.
Size of Baltimore's Colony: 84.
Reproduction: Pairs mate for life, generally, with a "divorce" rate of about 5 percent. Each pair can produce two eggs a season, laid four days apart. Eggs take 48 days to hatch.
The animals live, on average, from 15 to 20 years, though one zoo denizen is 30.
Diet: Fish, mostly. The amorous Baltimoreans feast on river smelt, farm-raised trout, squid and caplin, a kind of herring.